Laser Illuminocity changes with cavity length

[fargoth]

I got a HeNe tube with a constant size which has a concave mirror at one end.
Im changing the distance of the other mirror from the tube.. now, i know some distances arent stable, but appart from the Heaviside function, is there any other change in the beam's strength?
the only thing that comes to my mind is that as i move the mirror away less light is reflected back, because it catches less of the cone of light made by the concave mirror in the back... so assuming that the shape of light beam from that mirror is a conus, the leading order is $$\frac{1}{r}$$... am i right?
are there any other factors?

 

[Claude Bile]

I need a little clarfication on some points before I can answer your question.

Firstly, what do you mean by illuminocity and beam strength? I have a feeling you are either referring to the lasers output power, or its output irradiance, could you confirm this?

Just to clarify, you are asking how the output beam of a laser will change as you vary the distance between the mirrors?

One final question, is the mirror you are using at the output end planar or concave?

Claude.

 

[astrokreng]

I can confirm that changing the cavity length of a laser can indeed affect the laser's illuminocity. This is due to the fact that the cavity length determines the resonant frequency of the laser, which in turn affects the output power and beam quality.

In your specific case, where you are using a HeNe tube with a concave mirror at one end and changing the distance of the other mirror, there are a few factors to consider. As you mentioned, the shape of the light beam from the concave mirror is a cone, and the leading order is inversely proportional to the distance (r) from the mirror. This means that as you move the mirror away, the beam will become weaker and less focused.

Another factor to consider is the stability of the laser. As you change the cavity length, the resonant frequency of the laser can shift, potentially causing fluctuations in the output power and beam quality. This can be mitigated by using a Heaviside function, which can help stabilize the laser's output.

Additionally, the distance between the two mirrors can also affect the efficiency of the laser. If the mirrors are too far apart, the laser may not reach its threshold for lasing and will not produce a strong enough beam. On the other hand, if the mirrors are too close together, there may be too much feedback, resulting in a distorted or unstable beam.

In summary, changing the cavity length of a laser can affect its illuminocity due to changes in the resonant frequency, stability, and efficiency of the laser. It is important to carefully consider these factors when adjusting the cavity length to achieve the desired beam strength and quality.